Anyone destroy a catalytic converter by running rich?

[tekdeus]

Anyone destroy a catalytic converter by running rich? My car is tuned quite rich and I'm going to run a Magnaflow hi-flow cat. I read the text below from the Random Technology website: http://randomtechnology.com/technical.html

"Under normal operating conditions, the catalytic process doesn’t begin until temperatures inside a converter reach 500 to 600 degrees (F). If air/fuel ratio is on target, and the exhaust is free of contaminants, internal converter temperature stays at about 1200 degrees. But when unburned fuel enters the picture, temperatures can reach 2200 degrees and either burn the precious metals out of the washcoat, or literally cause a melt down of the bricks. Extremely high temperatures can also result in destruction of the mat that's wedged between the bricks to the converter case."

 

[hellraiser456]

yup...i have. not a high flow one though. but it can happen and is perhaps one of the main killers. however you have to be running pretty rich.

 

[dugums]

Is there a correlation between EGT's and catalytic converter temps?

It seems like there would be, but that paragraph seems to indicate the change in fuel mixture will cause the catalytic converter to raise in temperature - is this the result of chemical reaction with the catalytic element? A lean mixture should increase exhaust stream heat - yes? - so I am wondering what process causes the rich mixture to amplify the heat in the cat. I have not researched cats at all - maybe someone like JJ can chime in hear and help us out. This has me interested, so I'll do some digging and report back as well.

Anyway - before my rebuild the car was running VERY rich (I don't know for how long, as I just purchased it). The cat was toast - I'm assuming the rich mixture being the reason. Aaron at DM hooked me up with a high-flow unit and I got some tuning done - hopefully no more issues.

 

[jetjock]

Define rich. Moderately rich mixtures will not overheat a catalyst because the O2 content is very low under such conditions. An exhaust stream high in HC is a totally different story. Go rich to the point the engine is into rich misfire and you'll toast the cat. Note the words "unburned fuel" in the comments. They're talking about HC. You can have high HC in a lean mixture and melt the cat. In fact most cat meltdowns are caused by the combination of a lean mixture (high O2) and high HC.

 

[Mr. Sinister]

Yeah. I had one crap out after well less than 1K miles (probably less than 500). Car passed emissions, then 2 years later wouldn't pass anymore. Put a new cat on and it was good to go again.

 

[BlackMKIII]

*raises hand* And blew orange chunks into the street.

 

[tekdeus]

Define rich.

10.4-11 on average? Also, would the temporary surges of unburnt fuel caused by a BOV vented to atmosphere/AFM setup be a concern?

 

[IJ.]

My 3.5" MetalCat is looking pretty sad these days.

 

[Poodles]

I've done it...

OEM cats tend to take the heat better than the aftermarket cheapies that have a cheaper matrix...

they also don't like vibration, impact, ect... think of it as glass

 

[jetjock]

10-11 is fine as long as it's not sustained ie; it only happens at WOT. Catalyst temps are not static and always elevate after a short exposure to high HC levels. I won't bore you with the details but it's designed to handle such excursions both in temp and emissions control. After all, the engine runs pretty rich stock at WOT and doesn't burn up the factory cat. Mine is orignial and still works fine.

Besides, at the HC levels present in that mixture it'd take around 30 minutes for the cat to really get going. You don't drive at WOT for that long do you?

 

[tekdeus]

My 3.5" MetalCat is looking pretty sad these days.

Are metal cats designed to take more abuse than ceramic ones?

 

[IJ.]

Tek: Yes they're meant to be more robust ......

And they flow better for a given size but as I said mine looks pretty sad the matrix is concave when you look into the Cat.